Optimized production and characterization of highly porous activated carbon from algal-derived hydrochar

Abstract

Preparation of porous activated carbon from algal hydrochar obtained from hydrothermal carbonization, using chemical activation method has been conducted in this study. This study focused on the effects of different activation parameters as well as different chemical activators such as alkali activators, carbonate, acid and mixture of alkali activators on prepared activated carbon. Response surface methodology applying central composite design were employed to investigate the effects of activation temperature (525 ≤ T ≤ 825 °C), mass ratios of potassium hydroxide as an activator and hydrochar (0.3 ≤ R ≤ 2.7) and nitrogen flow rate (63 ≤ F ≤ 267 cm3/min) at constant heating rate of 3 °C/min on specific surface area and yield of the produced activated carbons. The chemically prepared activated carbons at optimum process conditions of T = 675 °C, R = 1.5 and F = 267 cm3/min, using potassium carbonate or potassium hydroxide as a chemical agent, revealed high surface area (≥2100 m2/g) with the maximum yield of 61.3 wt%, pore volume in the range of (1.2–1.5 cm3/g) and average pore size of (5.9–8.3 nm). Almost complete removal of methylene blue removal was achieved from a solution with methylene blue concentration of 250 mg/L, with chemically activated carbon dosage of 1 g/L within 5 min at room temperature.